Many structures are built using concrete, including, for instance, buildings, parking structures, apartments, condominiums, hotels, mixed-use, casinos, hospitals, medical buildings, government buildings, research/academic institutions, industrial, malls, bridges, pavement, tanks, reservoirs, silos, foundations, sports courts, and other structures.
Prestressed concrete is structural concrete in which internal stresses are introduced to reduce potential tensile stresses in the concrete resulting from applied loads; this can be accomplished by two methods—post-tensioned prestressing and pre-tensioned prestressing. In a post-tensioned member, the prestressing member is tensioned after the concrete has attained a specified strength. In post-tensioning applications, the prestressing assembly, commonly known as a tendon, may include for example and without limitation, anchorages, the prestressing member, and sheathes or ducts. For the purposes of this disclosure, the prestressing member will be referred to as a “cable”, although one having ordinary skill in the art with the benefit of this disclosure will understand that the prestressing member could be any suitable material exhibiting tensile strength which can be elongated including, for example and without limitation, reinforcing steel, single or multi strand cable. One having ordinary skill in the art with the benefit of this disclosure will likewise understand that the prestressing member may be formed from a metal or composite without deviating from the scope of this disclosure. The tendon generally includes an anchorage at each end. The cable is generally fixedly coupled to a fixed anchorage positioned at one end of the tendon, the so-called “fixed-end”, and is adapted to be stressed at the other anchor, the “stressing-end” of the tendon.
In order to allow access to the stressing-end of the tendon once the concrete member is poured, a pocket former may be utilized to, for example, prevent concrete from filling in the area between the stressing-end anchor and the concrete element used to form the concrete member. As understood in the art, the concrete element may be a form or mold into which concrete is poured or otherwise introduced into to give shape to the concrete as it sets or hardens thus forming the concrete member. Once the concrete has sufficiently hardened and the form is removed, the pocket former is removed from the concrete member. Generally, pocket formers are frustoconical in shape to, for example, allow for easier removal from the concrete member. Typically, once the tendon is stressed, the pocket formed by the pocket former is filled with a material such as a cementitious chloride-free grout or concrete to, for example, provide fire protection and corrosion protection.